Inertial sensors are useful in many devices, such as consumer mobile devices (e.g., smartphone, game controller, etc.). Gyroscopes are used as sensors of angular velocity or angular acceleration generated by rotation of a movable body and may be formed using MEMS manufacturing processes, which generally utilize semiconductor fabrication techniques. MEMS gyroscopes may include a suspended proof mass driven to mechanically vibrate in a first dimension relative to a support with the Coriolis effect coupling energy from the vibrating mass to an orthogonal (sensed) dimension when the gyroscope (disposed in the mobile device) experiences a rotation. A rotation rate (e.g., rad/sec) may then be determined. One or more such gyroscopes, when embedded within a mobile device, may then be utilized to characterize angles of rotation about a three dimensional axis (e.g., yaw, pitch, roll).
Many MEMS gyroscopes rely on a change in capacitance between the proof mass and the support resulting from the Coriolis force, measured, for example, by converting the magnitude of the capacitance to a voltage. As such, it is desirable to make capacitive coupling between the suspended proof mass and the support large by minimizing the physical spacing between surfaces of the proof mass and the support. For example, gap spacing between capacitively coupled faces of a suspended proof mass and the support may be on the orders of nanometers for the sake of greater sensor sensitivity. However, such dimensions rely on advanced thin film techniques, (e.g., conformal depositions, anisotropic plasma etches, etc.), necessitating fabrication of such inertial sensors as discrete devices, typically employing a silicon (e.g., MEMS) chip that is separated from a processor or other integrated circuit (IC) chip handling logic functions in the mobile device. Thus, integration of inertial sensors with other ICs is typically board-level.
Inertial sensors that can be integrated with ICs within a same package in a manner that does not require the package to be of a thickness significantly greater than it would otherwise are therefore advantageous, particularly for mobile device form factors.